Excavator and a machine for material transfer

ABSTRACT

The invention relates to an excavator or to a machine for material transfer comprising an element movable via at least one hydraulic cylinder. In accordance with the invention, one or more hydraulic cylinders are additionally hinged to the element, with the additional hydraulic cylinder(s) being connected to one or more hydraulic accumulators.

The invention relates to excavators and to machines for materialtransfer comprising an element movable via at least one hydrauliccylinder.

With excavators and machines for material transfer such as excavators,wheel-mounted loaders and similar plant, a boom and/or a shaft are movede.g. via two parallel hydraulic cylinder pairs. In the case of anexcavator, an attachment tool is then attached to the shaft and the goodto be loaded is transferred with it. Both the boom and the shaft and theattachment tools naturally have masses. This means that only a smallpart of the energy used for the lifting work benefits the lifting of theload. The much greater part must be used for the lifting of theequipment and of the attachment tool.

A detail of an excavator and of machines for material transfer inaccordance with the prior art is shown by way of example in FIG. 1. Itis an excavator in the present case. A boom 12 is hinged to a rotatingdeck 10 of an excavator here and is movable via two hydraulic cylinderpairs 14. The hydraulic cylinder pairs are connected together, as can beseen from the hydraulic circuit diagram in accordance with FIG. 1 a.

Some first efforts have already been made to recover the energy expendedin the lifting work of the equipment and of the attachment tool in anenergy recovering system. For this purpose, it was attempted, forexample in DE 102 56 442 A1 and DE 103 15 071 A1, to feed hydraulicallystored energy into the main hydraulic circuit. However, this is onlysuccessful with limitations since the infeed pressure must always belarger than the system pressure in the main circuit.

It is therefore the object of the present invention to provide anexcavator or a machine for material transfer in accordance with thepreamble of claim 1 in which a large part of the energy expended for thelifting of the equipment and of the attachment tool can, where possible,be stored for successive work cycles.

This object is solved in accordance with the invention in that, inaddition to the at least one hydraulic cylinder present for the movementof the movable elements, one or more additional hydraulic cylinders arehinged to the element to be moved, with the additional cylinder(s) beingconnected to one or more hydraulic accumulators of their own. Theseadditional hydraulic cylinders can be arranged parallel to the alreadypresent at least one hydraulic cylinder, but can also be attached at adifferent position. In accordance with the invention, the additionalhydraulic cylinders do not engage in the hydraulic system, but areconnected on the piston side with a hydraulic accumulator which canconsist of a piston accumulator or a bladder accumulator.

Advantageous aspects of the present invention result from thesubordinate claims dependent on the main claim.

The element to be moved can accordingly be a boom or a shaft of theexcavator or of the machine for material transfer.

The additional hydraulic cylinder(s) can be arranged between twohydraulic cylinders which serve to move the element, i.e. the boom orthe shaft.

In accordance with the invention, the accumulator is loaded on thedownward movement of the equipment. The stored energy then in turnsupports the upward movement of the equipment. The equipment weight canhereby be compensated at least partly. The same work is carried out viathe, for example, three cylinders now present instead of the twopreviously present as was previously carried out by the two hydrauliccylinders connected in the hydraulic circuit.

In accordance with a particularly advantageous embodiment of theinvention, the additional hydraulic cylinder(s) can be connectable tothe main hydraulic circuit of the excavator or machine for materialtransfer via a switchable valve. For example, for the case that thestorage system breaks down, the third cylinder can thus be switched intothe main hydraulic circuit via a valve so that the machine is not downand can carry out its work without a problem.

Furthermore, with a multi-element equipment and on the provision of morethan one additional hydraulic cylinder, the number of additionalhydraulic cylinders can advantageously be connected among one another.For example, on the downward movement of the boom, the additionalhydraulic cylinder of the shaft can thus be fed such that the shaft issupported on extension and vice versa.

The solution of the initially presented object in accordance with theinvention results in a series of advantages: The previously used mainhydraulic cylinders can thus be dimensioned smaller. Less energy fromthe diesel engine is necessary overall for the lifting. Higher workingspeeds are possible. The engine can theoretically have less power or, ifit has a higher power, it can work in the part load range. Less energyhas to be removed via the radiator overall. The machine efficiency canbe considerably increased. The fuel consumption can thus be lowered.This in turn results in a lowering of operating costs.

Moreover, the bearing strains of the hydraulic cylinders can also bedistributed onto six bearing positions instead of the usual four. Due tothe provision of accumulator(s) of its/their own for the additionalhydraulic cylinder(s), an active feeding into the main hydraulic circuitis not necessary. No complex hydraulic connections are therebynecessary.

The processes of feeding energy into the additional hydrauliccylinder(s) are possible at any pressure level. No consideration has tobe made of the pressure level of the main hydraulic circuit here.Finally, system redundancy is given by switching the additionalhydraulic cylinder(s) over to the main hydraulic circuit.

Further features, details and advantages of the invention result fromthe embodiments shown in the drawing. There are shown:

FIG. 1: a detail view of a part of an excavator or of a machine formaterial transfer in accordance with the prior art;

FIG. 2: a representation in accordance with FIG. 1 in accordance with anembodiment variant of the present invention (including the hydrauliccircuit diagram); and

FIG. 3: a schematic hydraulic circuit diagram of a variant of theembodiment in accordance with FIG. 2.

A detail of a hydraulic excavator is shown with reference to FIG. 2 byway of example for an excavator and machines for material transfer.Here, a boom 12 is pivotably hinged to a rotating deck 10, with thepivoting up and down of the boom 12 taking place via hydraulic cylinders14. In addition to the hydraulic cylinders 14, an additional hydrauliccylinder 16 is arranged centrally. It can be seen from the hydrauliccircuit diagram in accordance with FIG. 2 a that the hydraulic cylinders14 are connected to one another in a similar manner to that alreadyknown from the prior art (cf. FIG. 1 a). In addition to the hydrauliccylinders 14, an additional hydraulic cylinder 16 is provided whosepiston side 18 is connected to a hydraulic accumulator 20 which can, forexample, be a piston accumulator or a bladder accumulator.

As can be seen from the hydraulic circuit in accordance with FIG. 2 a,the additional hydraulic cylinder 16 is independent of the hydrauliccylinders 14. The hydraulic. cylinder 16 serves the purpose of thehydraulic fluid being displaced in the direction toward the hydraulicaccumulator 20 by the piston 22 on a downward movement of the equipment.The energy is stored here until the boom 12 should again be movedupwardly. Here, the energy stored in the accumulator 20 is releasedagain by means of the additional hydraulic cylinder 16 so that a largepart of the mass force of the boom and of the shaft or equipmentsuspended thereon is compensated and no longer has to be expended by thehydraulic cylinders 14.

In the hydraulic circuit diagram in accordance with FIG. 3, there is abasically similar embodiment variant as in the hydraulic circuit diagramin accordance with the embodiment variant of FIG. 2 a. Here, however, aselective connection with the main hydraulic circuit, via which thehydraulic cylinders 14 are supplied, is possible via correspondingswitch valves 22 and 24 for the additional hydraulic cylinder 16, whichis here likewise connected to a hydraulic accumulator 20. The additionalhydraulic cylinder 16 can therefore be connected into the main hydrauliccircuit depending on the position of the valves 22 and 24. This may, forexample, be desired when the accumulator 20 is defective and when thehydraulic excavator should continue to work continuously despite thisdefect until it can be repaired.

1. An excavator or a machine for material transfer comprising an elementmovable via at least one hydraulic cylinder, and at least one hydrauliccylinder additionally hinged to the element, the additional hydrauliccylinder being connected to one or more hydraulic accumulators.
 2. Anexcavator or a machine for material transfer in accordance with claim 1,wherein the element is a boom or shaft of an excavator or a machine formaterial transfer.
 3. An excavator or a machine for material transfer inaccordance with claim 1, wherein the additional hydraulic cylinder(s)are arranged between or outside one or more hydraulic cylinders whichserve the movement of the element.
 4. An excavator or a machine formaterial transfer in accordance with claim 1, wherein the additionalhydraulic cylinder(s) is/are connectable to the main hydraulic circuitof the excavator or machine for material transfer via a switchablevalve.
 5. An excavator or a machine for material transfer in accordancewith claim 1, wherein, with equipment consisting of a plurality ofelements, a plurality of additional hydraulic cylinders are connected toone another and are connected to a hydraulic accumulator.
 6. Anexcavator or a machine for material transfer in accordance with claim 1,wherein one of the two hydraulic cylinders present is connected to oneor more hydraulic accumulators.
 7. An excavator or a machine formaterial transfer in accordance with claim 2, wherein the additionalhydraulic cylinder(s) are arranged between or outside one or morehydraulic cylinders which serve the movement of the element.
 8. Anexcavator or a machine for material transfer in accordance with claim 7,wherein the additional hydraulic cylinder(s) is/are connectable to themain hydraulic circuit of the excavator or machine for material transfervia a switchable valve.
 9. An excavator or a machine for materialtransfer in accordance with claim 2, wherein the additional hydrauliccylinder(s) is/are connectable to the main hydraulic circuit of theexcavator or machine for material transfer via a switchable valve. 10.An excavator or a machine for material transfer in accordance with claim3, wherein the additional hydraulic cylinder(s) is/are connectable tothe main hydraulic circuit of the excavator or machine for materialtransfer via a switchable valve.
 11. An excavator or a machine formaterial transfer in accordance with claim 10, wherein, with equipmentconsisting of a plurality of elements, a plurality of additionalhydraulic cylinders are connected to one another and are connected to ahydraulic accumulator.
 12. An excavator or a machine for materialtransfer in accordance with claim 2, wherein, with equipment consistingof a plurality of elements, a plurality of additional hydrauliccylinders are connected to one another and are connected to a hydraulicaccumulator.
 13. An excavator or a machine for material transfer inaccordance with claim 3, wherein, with equipment consisting of aplurality of elements, a plurality of additional hydraulic cylinders areconnected to one another and are connected to a hydraulic accumulator.14. An excavator or a machine for material transfer in accordance withclaim 4, wherein, with equipment consisting of a plurality of elements,a plurality of additional hydraulic cylinders are connected to oneanother and are connected to a hydraulic accumulator.
 15. An excavatoror a machine for material transfer in accordance with claim 7, wherein,with equipment consisting of a plurality of elements, a plurality ofadditional hydraulic cylinders are connected to one another and areconnected to a hydraulic accumulator.
 16. An excavator or a machine formaterial transfer in accordance with claim 8, wherein, with equipmentconsisting of a plurality of elements, a plurality of additionalhydraulic cylinders are connected to one another and are connected to ahydraulic accumulator.
 17. An excavator or a machine for materialtransfer in accordance with claim 9, wherein, with equipment consistingof a plurality of elements, a plurality of additional hydrauliccylinders are connected to one another and are connected to a hydraulicaccumulator.
 18. An excavator or a machine for material transfer inaccordance with claim 10, wherein, with equipment consisting of aplurality of elements, a plurality of additional hydraulic cylinders areconnected to one another and are connected to a hydraulic accumulator.19. An excavator or a machine for material transfer in accordance withclaim 18, wherein one of the two hydraulic cylinders present isconnected to one or more hydraulic accumulators.
 20. An excavator or amachine for material transfer in accordance with claim 2, wherein one ofthe two hydraulic cylinders present is connected to one or morehydraulic accumulators.